One foci is to perform a genome wide association study in patient with COPD to identify novel genetic markers for the patient subgroups who report different experiences with the symptom cluster of pain, fatigue, breathlessness, sleep disturbance, and depression. It is likely that genetic and immunologic factors may be involved in symptom severity and morbidity. Specifically, low levels of circulating immunoglobulins have been observed in a subset of COPD patients. Although hypogammaglobulinemia (HGG) is known to lead to frequent airway infections in other patients groups, the relationship between HGG and clinical symptoms in COPD has not been studied. The resulting knowledge can help clinicians to better identify COPD patients at particular risk for severe single and multiple symptoms.